There has been technologies for constructing a system including a plurality of relay apparatuses to distribute processing load on a relay apparatus transferring data (referred to as message data) of a message exchanged between a client and an application (APL) server.
FIG. 27 illustrates an example of a system including a plurality of relay apparatuses. In FIG. 27, when a load balancer (LB) or the like receives message data from a client, the LB distributes the received message data to one of the relay apparatuses by using various types of load balancing algorithms. Upon receiving the message data received from the LB, the relay apparatus accesses an external device and acquires transfer rules to perform message transfer in accordance with the acquired transfer rules. In the system illustrated in FIG. 27, the external device performs centralized control of the transfer rules. Thus, the system may perform message transfer such that a series of message data including identical identifier (ID) data, for example, is transferred to the same APL server. In the present application, such message transfer is referred to as message transfer ensuring the uniqueness of a transfer destination.
Alternatively, each of the relay apparatuses included in the system may hold data of identical transfer rules to ensure the uniqueness of a transfer destination.